Mamun Abdullah Al, Yuzhen Ming, Dandan Zhang et al.
Purpose Denitrifying bacteria perform a crucial ecological process regulating nitrogen cycling and greenhouse gas emissions. However, the community assembly mechanisms of nitric oxide producing denitrifying bacteria, particularly abundant and rare communities, are poorly understood. Materials and methods In this study, nirK- and nirS marker genes were amplified following 16S rRNA sequencing, with the aim to identify the mechanisms shaping abundant and rare nirK- and nirS-type denitrifying bacteria in Taihu Lake sediments, particularly regarding the heterogeneity of a wide range of environmental factors. Results Taihu Lake sediment showed low-pollution levels of heavy metals, but with significant differences of high nutrient status. The phylogenetic diversity of nirK- and nirS-type denitrifying bacteria, and beta-diversity of abundant and rare communities were affected by a combined stressor of heavy metals and nutrients. Our results revealed that rare denitrifying bacteria had significantly higher homogeneity of dispersal than that of abundant taxa. We found heterogeneous selection was the main process governing both abundant and rare nirK-type denitrifying bacteria, while the abundant nirS-type denitrifying bacteria were mainly governed by the dispersal limitation. Complex network interactions between abundant and rare nirK- and nirS-type denitrifying bacteria were detected, further the Mantel test showed strong significant correlations between keystone denitrifying bacteria with environmental factors. Conclusion This study provides insights into the effects of nutrient pollution on denitrifying bacteria in lake sediment, and also enhances our understanding of community assembly mechanisms of abundant and rare nirK- and nirS-type denitrifying bacteria in lake ecosystems.
Mamun Abdullah Al, Yunfeng Wang, Jie Huang et al.
Anammox and denitrifcation are key processes for nitrogen removal in lake sediments. However, how environmental
changes mediate the community structure and functional genes of nitrogen removal bacteria in lakes remain unclear. Using
metagenome and amplicon sequencing, we investigated the anammox and denitrifying bacteria and their nitrogen removing potentials in lakes experiencing signifcant spatiotemporal and environmental variations. The community structure of
anammox and denitrifying bacteria exhibited stronger lake-wide spatial variations than that of seasonality, while only the
denitrifcation-related functional genes showed substantial variations in both lakes. Anammox genes (e.g., hzsA/B/C and hdh)
showed no signifcant spatial variations. However, the abundances of anammox and denitrifying genes were signifcantly
higher in winter than in summer. The mesotrophic Lake Weishan demonstrated a greater capacity for complete denitrifcation
in winter, while the eutrophic Lake Donghu exhibited a higher potential of anammox in summer. Diferences in functional
gene abundances between lakes were more pronounced than variations in phylogenetic diversity, indicating clear functional
adaptations to local environments. The coupled nitrogen removal potentials also refected ecological interactions among
anammox and denitrifying genes. Importantly, anammox and denitrifying bacterial communities and their functional genes
were primarily driven by dissolved organic carbon, total phosphorous and zinc (Zn). The dissimilarities of anammox and
denitrifying bacterial communities increased with geographic distance, indicating a clear distance-decay efect. This study
highlights the anammox and denitrifying bacteria and their nitrogen removal potentials in lake sediments that are mediated
by both spatial and seasonal environmental changes.
Mamun Abdullah Al, Dandan Zhang, Sirui Liu et al.
Denitrifying bacteria, particularly nirK- and nirS-type, are functionally equivalent and could occupy diferent niches, but
their community assembly mechanisms and responses to environmental heterogeneity are poorly understood in eutrophic
lakes. In this study, we investigated the community assembly mechanisms of nirK- and nirS-type denitrifying bacteria
and clarifed their responses to sediments environmental factors in Lake Taihu, China. The quantitative real-time PCR
and Illumina HiSeq-based sequencing revealed that the abundance and composition of two types of denitrifying bacterial
communities varied among diferent sites in the sediments of Lake Taihu. The functions of these two types of denitrifying
bacteria were assigned to mainly nitrogen cycling along with carbon, oxygen, and sulfur cycling, indicating their diverse
ecosystems functions. Neutral community model showed that majority of nirK- and nirS-type denitrifying bacteria were
neutrally distributed, while dispersal and selection were the dominant drivers in shaping community assembly of nirK-type
bacteria. The community assembly of nirS-type was mainly driven by homogeneous selection. We found complex network
interactions between nirK- and nirS-type denitrifying bacteria with other bacterial communities, indicating the importance
of other bacterial coexistence for ecosystem functions by denitrifying bacteria in lake sediments. Keystone taxa of other
bacteria showed the highest interactions with denitrifying bacteria; further, a strong signifcant correlation between keystone
taxa with environmental factors and sediment enzyme content revealed by Mantel tests. Specially, total phosphorous was
the key environmental factor determining the composition and diversity of nirK and nirS-type denitrifying bacteria in lake
sediments, whereas NAR, AmoA, and NIR were the key reductase enzymes directly or indirectly afected to them. Our results
provide signifcant insights into understanding the efects of changing nirK- and nirS-type denitrifying bacterial diversities
and underlying community assembly mechanisms under changing environmental conditions in eutrophic lake ecosystems.
Abdul Rehman, Th´ eog`ene Habumugisha, Fuyi Huang et al.
Aquatic environments are frequently contaminated with nanoplastics (NPs) ranging from 1–100 nm generated by
plastic aging, but their bio-enrichment and toxicological impacts remain poorly understood. This study investigates how chronic exposure to carboxylated polystyrene nanoplastics (PNPs) alters gut microbiota
composition and function in zebrafsh (Danio rerio). Adult zebrafsh were exposed to 50 nm PNPs at concentrations of 0.1, 1.0, and 10 mg/L for 14 and 28 days, followed by gut microbiota analysis using 16S rRNA gene
sequencing. PNP exposure altered gut microbiota composition, including an increase in Proteobacteria abundance and a decrease in Firmicutes, Bacteroidetes, and the inflammation-related genus Alistipes. Benefcial
probiotics such as Faecalibacterium, Streptococcus, Bifdobacterium, and Lachnospira were diminished, while
pathogenic bacteria proliferated. TEM imaging revealed the internalization of PNP particles within intestinal
tissues resulted in vacuolation, suggesting potential epithelial damage. Co-occurrence network patterns of gut
microbiota greatly decreased during treatment with NPs. The neutral community model showed that among PNP
treatments, 0.1 mg/L led to a less predictable (stochastic assembly process). PNP exposure led to increased
predicted microbial functions (via PICRUSt2) related to xenobiotic metabolism, infection pathways, and lipopolysaccharide (LPS) production, while RNA transport and N-glycan biosynthesis were decreased. However,
pathways related to microbial antioxidants exhibited signifcant variation across different PNP levels. These
results provide critical insights into the toxicological impacts of chronic PNP exposure on fsh gut health,
highlighting the potential risks to aquatic ecosystems and human health.
4. Abdullah Al M, Chen HH, Yan X et al.
High-throughput sequencing has revolutionized the DNA sequence-based study of microbial community and
diversity on an unprecedented scale. Relic DNA is widespread in the natural aquatic environment; however, the
extent to which such DNA can bias the sequence-based analysis of living microeukaryotic communities is unclear.
Here, we conducted a 30-day feld-control experiment investigating bioflm succession of microeukaryotic
communities on glass slides and polyurethane foam units (PFUs) in a subtropical urban reservoir, using DNAbased approach. The propidium monoazide (PMA) dye was used to distinguish living and relic DNA sequences. Our results showed that microeukaryotic community succession in bioflms was time and substratum
dependent, which was correlated with changing environmental conditions, nutrients and microalgae. Most
importantly, relic DNA has a signifcant influence on the estimation of beta diversity and turnover in community
composition, importantly its presence masked the successional patterns of different microbial taxa. We found
strong deterministic processes dominating microeukaryotic succession on glass slides and PFUs bioflms.
Depending on substrate and the presence and absence of relic DNA sequences, contrasting community assembly
mechanisms were observed. In the presence of relic DNA, our results showed that 0.53–3.15 % of dispersal
limitation, and 13.16 % of homogeneous selection processes were overestimated, while 1.06–3.68 % of homogenizing dispersal, 2.11–10.53 % of undominated and 2.10–10.52 % of heterogeneous selection processes
were underestimated. This study provides signifcant insights into the value of removing relic DNA when
designing DNA-based studies to characterize microeukaryotic communities and raise questions about some
ecological interpretations in molecular microbial ecology which have not accounted for the effects of relic DNA.
Yan X, Li S, Abdullah Al M et al.
Changes in salinity have a profound influence on ecological services and functions of inland freshwater ecosystems, as well as on the shaping of microbial communities. Bacterioplankton, generally classifed into freeliving (FL) and particle-attached (PA) forms, are main components of freshwater ecosystems and play key
functional roles for biogeochemical cycling and ecological stability. However, there is limited knowledge about
the responses of community stability of both FL and PA bacteria to salinity fluctuations. Here, we systematically
explored changes in community stability of both forms of bacteria based on high-frequency sampling in a shallow
urban reservoir (Xinglinwan Reservoir) in subtropical China for 3 years. Our results indicated that (1) salinity
was the strongest environmental factor determining FL and PA bacterial community compositions – rising
salinity increased the compositional stability of both bacterial communities but decreased their α-diversity. (2)
The community stability of PA bacteria was signifcantly higher than that of FL at high salinity level with low
salinity variance scenarios, while the opposite was found for FL bacteria, i.e., their stability was higher than PA
bacteria at low salinity level with high variance scenarios. (3) Both bacterial traits (e.g., bacterial genome size
and interaction strength of rare taxa) and precipitation-induced factors (e.g., changes in salinity and particle)
likely contributed collectively to differences in community stability of FL and PA bacteria under different salinity
scenarios. Our study provides additional scientifc basis for ecological management, protection and restoration of
urban reservoirs under changing climatic and environmental conditions.
Yuzhen Ming, Mamun Abdullah Al, Dandan Zhang et al.
Denitrification is a crucial process in the global nitrogen cycle, in which two functionally equivalent genes, nirS and nirK, catalyse the critical reaction and are usually used as marker genes. The nirK gene can function independently, whereas nirS
requires additional genes to encode nitrite reductase and is more sensitive to environmental factors than nirK. However, the ecological differentiation mechanisms
of those denitrifying microbial communities and their adaptation strategies to environmental stresses remain unclear. Here, we conducted metagenomic analysis for
sediments and bioreactor samples from Lake Donghu, China. We found that nirStype denitrifying communities had a significantly lower horizontal gene transfer
frequency than that of nirK-type denitrifying communities, and nirS gene phylogeny
was more congruent with taxonomy than that of nirK gene. Metabolic reconstruction of metagenome-assembled genomes further revealed that nirS-type denitrifying communities have robust metabolic systems for energy conservation, enabling
them to survive under environmental stresses. Nevertheless, nirK-type denitrifying communities seemed to adapt to oxygen-limited environments with the ability to utilize various carbon and nitrogen compounds. Thus, this study provides
novel insights into the ecological differentiation mechanism of nirS and nirK-type
denitrifying communities, as well as the regulation of the global nitrogen cycle and
greenhouse gas emissions.
Li S, Yan X, Abdullah Al M et al.
Microbiomes are integral to ecological health and human well-being;
however, their ecological and evolutionary drivers have not been systematically
investigated, especially in urban park ecosystems. As microbes have different levels of
tolerance to environmental changes and habitat preferences, they can be categorized
into habitat generalists and specialists. Here, we explored the ecological and evolutionary characteristics of both prokaryotic and microeukaryotic habitat generalists and
specialists from six urban parks across fve habitat types, including moss, soil, tree hole,
water, and sediment. Our results revealed that different ecological and evolutionary
processes maintained and regulated microbial diversity in urban park ecosystems. Under
ecological perspective, community assembly of microbial communities was mainly
driven by stochastic processes; however, deterministic processes were higher for habitat
specialists than generalists. Microbial interactions were highly dynamic among habitats,
and habitat specialists played key roles as module hubs in intradomain networks.
In aquatic interdomain networks, microeukaryotic habitat specialists and prokaryotic
habitat specialists played crucial roles as module hubs and connectors, respectively.
Furthermore, analyzing evolutionary characteristics, our results revealed that habitat
specialists had a much higher diversifcation potential than generalists, while generalists
showed shorter phylogenetic branch lengths as well as larger genomes than specialists.
This study broadens our understanding of the ecological and evolutionary features of
microbial habitat generalists and specialists in urban park ecosystems across multi-habitat.
IMPORTANCE Urban parks, as an important urban greenspace, play essential roles in
ecosystem services and are important hotspots for microbes. Microbial diversity is driven
by different ecological and evolutionary processes, while little is currently known about
the distinct roles of ecological and evolutionary features in shaping microbial diversity in urban park ecosystems. We explored the ecological and evolutionary characteristics of prokaryotic and microeukaryotic habitat generalists and specialists in urban
park ecosystems based on a representative set of different habitats. We found that
different ecological and evolutionary drivers jointly maintained and regulated microbial diversity in urban park microbiomes through analyzing the community assembly
process, ecological roles in hierarchical interaction, and species diversifcation potential. These fndings signifcantly advance our understanding regarding the mechanisms
governing microbial diversity in urban park ecosystems.
Proshad R, Rahim AB, Rahman MM et al.
The world’s largest mangrove forest (Sundarbans) is facing an imminent threat from heavy metal pollution,
posing grave ecological and human health risks. Developing an accurate predictive model for heavy metal
content in this area has been challenging. In this study, we used machine learning techniques to model sediment pollution by heavy metals in this vital ecosystem. We collected 199 standardized sediment samples to predict the
accumulation of eleven heavy metals using ten different machine learning algorithms. Among them, the
extremely randomized tree model exhibited the best performance in predicting Fe (0.87), Cr (0.89), Zn (0.85), Ni
(0.83), Cu (0.87), Co (0.62), As (0.68), and V (0.90), achieving notable R2 values. On the other hand, the random
forest outperformed for predicting Cd (0.72) and Mn (0.91), whereas the decision tree model showed the best
performance for Pb (0.73). The feature attribute analysis identifed Fe–V, Cr–V, Cu–Zn, Co–Mn, Pb–Cd, and
As–Cd relationships resembled with correlation coeffcients among them. Based on the established models, the
prediction of the contamination factor of metals in sediments showed very high Cd contamination (CF ≥ 6). The
Moran’s I index for Cd, Cr, Pb, and As were 0.71, 0.81, 0.71, and 0.67, respectively, indicating strong positive
spatial autocorrelation and suggesting clustering of similar contamination levels. Conclusively, this research
provides a comprehensive framework for predicting heavy metal sediment pollution in the Sundarbans, identifying key areas needing urgent conservation. Our fndings support the adoption of integrated management
strategies and targeted remedial actions to mitigate the harmful effects of heavy metal contamination in this vital
ecosystem.
Zhang D, Liu F, Abdullah Al M et al.
Microorganisms play important roles in the biogeochemical cycles of lake sediment. However, the integrated
metabolic mechanisms governing nitrogen (N) and sulfur (S) cycling in eutrophic lakes remain poorly understood. Here, metagenomic analysis of feld and bioreactor enriched sediment samples from a typical eutrophic
lake were applied to elucidate the metabolic coupling of N and S cycling. Our results showed signifcant diverse
genes involved in the pathways of dissimilatory sulfur metabolism, denitrifcation and dissimilatory nitrate
reduction to ammonium (DNRA). The N and S associated functional genes and microbial groups generally
showed signifcant correlation with the concentrations of NH4 +, NO2 − and SO4 2, while with relatively low effects
from other environmental factors. The gene-based co-occurrence network indicated clear cooperative interactions between N and S cycling in the sediment. Additionally, our analysis identifed key metabolic processes,
including the coupled dissimilatory sulfur oxidation (DSO) and DNRA as well as the association of thiosulfate
oxidation complex (SOX systems) with denitrifcation pathway. However, the enriched N removal microorganisms in the bioreactor ecosystem demonstrated an additional electron donor, incorporating both the SOX
systems and DSO processes. Metagenome-assembled genomes-based ecological model indicated that carbohydrate metabolism is the key linking factor for the coupling of N and S cycling. Our fndings uncover the
coupling mechanisms of microbial N and S metabolism, involving both inorganic and organic respiration
pathways in lake sediment. This study will enhance our understanding of coupled biogeochemical cycles in lake
ecosystems.
Abdullah Al M, Wang WP, Jin L et al.
It is well-established that environmental variability and cyanobacterial blooms have major effects on the assembly and
functioning of bacterial communities in both marine and freshwater habitats. It remains unclear, however, how the
ciliate community responds to such changes over the long-term, particularly in subtropical lake and reservoir ecosystems. We analysed 9-year planktonic ciliate data series from the surface water of two subtropical reservoirs to elucidate
the role of cyanobacterial bloom and environmental variabilities on the ciliate temporal dynamics. We identified five
distinct periods of cyanobacterial succession in both reservoirs. Using multiple time-scale analyses, we found that the
interannual variability of ciliate communities was more strongly related to cyanobacterial blooms than to other environmental variables or to seasonality. Moreover, the percentage of species turnover across cyanobacterial bloom and
non-bloom periods increased significantly with time over the 9-year period. Phylogenetic analyses further indicated
that 84 %–86 % of ciliate community turnover was governed by stochastic dispersal limitation or undominated processes, suggesting that the ciliate communities in subtropical reservoirs were mainly controlled by neutral processes.
However, short-term blooms increased the selection pressure and drove 30 %–53 % of the ciliate community turnover.
Xue YY, Abdullah Al M, Chen HH et al.
Numerous studies have investigated the spatiotemporal variability in water microbial communities, yet the effects of relic DNA on microbial community profiles, especially microeukaryotes, remain far from fully understood. Here, total and active
bacterial and microeukaryotic community compositions were characterized using
propidium monoazide (PMA) treatment coupled with high-throughput sequencing in
a river-reservoir ecosystem. Beta diversity analysis showed a significant difference in
community composition between both the PMA untreated and treated bacteria and
microeukaryotes; however, the differentiating effect was much stronger for microeukaryotes. Relic DNA only resulted in underestimation of the relative abundances
of Bacteroidota and Nitrospirota, while other bacterial taxa exhibited no significant
changes. As for microeukaryotes, the relative abundances of some phytoplankton (e.g.
Chlorophyta, Dinoflagellata and Ochrophyta) and fungi were greater after relic DNA
removal, whereas Cercozoa and Ciliophora showed the opposite trend. Moreover,
relic DNA removal weakened the size and complexity of cross-trophic microbial networks and significantly changed the relationships between environmental factors and
microeukaryotic community composition. However, there was no significant difference in the rates of temporal community turnover between the PMA untreated and
treated samples for either bacteria or microeukaryotes. Overall, our results imply that
the presence of relic DNA in waters can give misleading information of the active microbial community composition, co-occurrence networks and their relationships with
environmental conditions. More studies of the abundance, decay rate and functioning
of nonviable DNA in freshwater ecosystems are highly recommended in the future.
Abdullah Al M, Xue YY, Xu J et al.
Urban freshwater ecosystems have important ecosystem functions, provide habitats for diverse microbial communities and are susceptible to multiple interconnected factors such as environmental pollution. Despite the
ecological signifcance of bacteria and microeukaryotes, little is known about how their community assembly
responds to various environmental factors across water and sediment habitats and ecological processes shaping
them. Here, environmental DNA-based approaches were used to investigate the community assembly processes
of bacteria and microeukaryotes (including habitat generalists and specialists) in urban water and sediment
across an urban-pollution gradient in Wuhan, central China. The diversity, community composition and potential
function of bacteria and microeukaryotes showed signifcantly stronger variation between water and sediment
than across an urban pollution gradient. Although, bacterial and microeukaryotic community assemblies were
dominated by strong selection processes in both water and sediment habitats, but a contrasting community
assembly mechanism was identifed between habitat generalists and specialists. Bacterial and microeukaryotic
communities showed a greater response to physicochemical variability in water, while a strong distance-decay
relationship was found in sediment. Further, cross-kingdom microbial network analysis revealed strong
modular associations of bacteria and microeukaryotes, meanwhile, microeukaryotic habitat specialists might be
keystone, but generalists have higher proportion of connections in the networks. This study provides signifcant
insights into the response of bacteria and microeukaryotes to different urban pollutions between water and
sediment, and the ecological processes structuring microbial community dynamics across habitat types under
anthropogenic disturbances.
Abdullah Al M, Akhtar A, Abu Hena MK et al.
Many human activities can greatly influence and alter the health of aquatic ecosystems. In this regard, the
quantitative analysis of macroinvertebrates and their relationships with ecological variables is an effective
method in environmental monitoring programs. Here, we used the benthic macroinvertebrate community as
bioindicators for assessing anthropogenic impacts on coastal waters in southeast Bangladesh. Sediment samples
were collected seasonally from three different sites influenced either by mangrove forests, aquaculture activity or
sewage input. The indicator value index (IndVal) analysis revealed 23 species of benthic macroinvertebrates as
potential bioindicators namely Enigmonia aenigmatica, Mactra chinensis and Pharella javanica of the class Bivalvia;
Tubifex tubifex of the class Clitellata; Lithopoma brevispina, Bullia vittata, Pomacea maculata and Umbonium vestiarium of the class Gastropoda; Gammarus roeselii of the class Malacostraca; and Amphicteis gunneri, Amphitrite
ornata, Aricidea simplex, Cirratulus cirratus, Heterospio catalinensis, Hypereteone foliosa, Lopadorrhynchus henseni,
Neanthes chingrighattensis, Micronephthys oligobranchia, Nephtys hombergii, Nereis jacksoni, Nereis zonata, Polyodontes maxillosus and Stygocapitella subterranean of the class Polychaeta. Their composition across three sites
varied signifcantly (P < 0.05) due to influence of environmental conditions as inferred from redundancy
analysis. Polychaeta, Gastropoda and Malacostraca were susceptible to sewage input, while Bivalvia and Clitellata were susceptible to aquaculture effluent. The results of this baseline study suggest that the identifed
benthic macroinvertebrate species can potentially be used to monitor anthropogenic disturbances in the marine
environment.
Ndayishimiye JC, Mazei Y, Babeshko K et al.
Global urbanization has resulted in local habitat fragmentation, infuencing ecological processes and biodiversity conservation. However, little is known about the diversity and distribution of microbial communities across urban biotopes. Here,
we compared testate amoeba communities in Moscow (63 samples from fve urban parks) and Xiamen (69 samples from six
urban parks) across four biotopes (tree hole, moss, soil, and sediment) to better understand microbial diversity and ecological
processes shaping microbial communities. A total of 116 morphospecies (31 genera), corresponding to 90 in Moscow and
84 in Xiamen, were identifed using light microscopy. The species richness per sample (mean ± standard error) was higher
in Moscow parks (14 ± 1 species, n = 63) than Xiamen parks. The mean species richness per biotope was highest in the
mosses (13 ± 1 species, n = 33). 13–26% of the total species richness was shared by all biotopes, indicating the ubiquitous
distribution of testate amoeba morphospecies. The community composition in diferent biotopes markedly difered in both
Moscow and Xiamen regions. Community connectivity varied among biotopes, and community complexity and dynamics
were substantially stronger in soil and sediment. The stochastic processes explained a signifcantly high percentage of community composition in all biotopes (57–81%) in 11 parks. The standardized efect size for C-score in all biotopes changed
from 1.48 to 6.92, indicating the enhanced signifcance of deterministic processes for the testate amoeba communities. The
diferent relative importance of stochastic or deterministic processes in four studied biotopes suggests that factors infuencing
the testate amoeba communities greatly vary across heterogeneous urban environments.
Mo YY, Peng F, Jeppesen E et al.
Aquatic biodiversity is important in mediating ecosystem functioning, contributing to ecosystem sustainability and
human wellbeing. However, how microbial network complexity affects the biodiversity-nutrient cycling relationship
in saline freshwater ecosystems remains underexplored. Using high-resolution time-series data, we examined the relationships between microeukaryotic-bacterial community network complexity, biodiversity and multi-nutrient cycling
in an urban reservoir undergoing a freshwater salinization-desalinization cycle. We found that low microbial diversity
enhanced ecosystem multi-nutrient cycling under high salinity stress. In addition, multi-nutrient cycling declined with
increased network complexity. Further, we found a non-linear relationship between salinity-induced shifts in the complexity of the microbial network and biodiversity-nutrient cycling (BNC) relationship of keystone taxa, i.e. the strength
of the BNC relationship first became weak and then strong with increased network complexity. Together, these results
highlighted the significant insight that there is not always positive relationship between biodiversity/network complexity and multi-nutrient cycling, even between network complexity and BNC relationship in real-world ecosystems,
suggesting that preserving microbial association is important in aquatic health managing and evaluating the freshwater salinization problem.
Proshad R, Uddin M, Idris AM et al.
Toxic metals in river sediments may represent significant ecological concerns, although there has been limited research on the source-oriented ecological hazards of metals in sediments. Surface sediments from an industrial affected
Rupsa River were utilized in this study to conduct a complete investigation of toxic metals with source-specific ecological risk assessment. The findings indicated that the average concentration of Ni, Cr, Cd, Zn, As, Cu, Mn and Pb were
50.60 ± 10.97, 53.41 ± 7.76, 3.25 ± 1.73, 147.76 ± 36.78, 6.41 ± 1.85, 59.78 ± 17.77, 832.43 ± 71.56 and 25.64
± 7.98 mg/kg, respectively and Cd, Ni, Cu, Pb and Zn concentration were higher than average shale value. Based on
sediment quality guidelines, the mean effective range median (ERM) quotient (1.29) and Mean probable effect level
(PEL) quotient (2.18) showed medium-high contamination in sediment. Ecological indexes like toxic risk index
(20.73), Nemerow integrated risk index (427.59) and potential ecological risk index (610.66) posed very high sediment pollution. The absolute principle component score-multiple linear regression (APCS-MLR) and positive matrix
factorization (PMF) model indicated that Zn (64.21%), Cd (51.58%), Cu (67.32%) and Ni (58.49%) in APCS-MLR
model whereas Zn (49.5%), Cd (52.7%), Cu (57.4%) and Ni (44.6%) in PMF model were derived from traffic emission,
agricultural activities, industrial source and mixed sources. PMF model-based Nemerow integrated risk index (NIRI)
reported that industrial emission posed considerable and high risks for 87.27% and 12.72% of sediment samples.
Abdullah Al M, Xue YY, Xiao P et al.
Biological monitoring and assessment are the frst and most fundamental steps towards diagnosing ecological or
environmental quality. Increasing anthropogenic impact on urban ecosystems has prompted the development of
less expensive and more effcient bioassessment approaches. Generally, a morphospecies based approach is
effective for plants and large organisms but challenging for the microbial biosphere. To overcome this challenge,
we used high-throughput DNA sequencing for predicting anthropogenic effects on microeukaryotic communities
in urban waterbodies along a pollution gradient in Wuhan City, central China in summer 2019. Our results
indicated that microeukaryotic community structure was distinct between non-urban polluted reservoir and
urban polluted waterbodies. The heterogeneity of environmental condition signifcantly affected the microeukaryotic diversity, community structure, and species interactions. Integrated co-occurring network analysis
revealed that the pollution gradient has a signifcant adverse impact on network complexity and network
dissimilarity. These results revealed that the signifcant variation in anthropogenically-driven environmental
condition shaped microeukaryotic communities in urban freshwater ecosystems. Furthermore, we observed that
the relative abundance of indicative OTUs were signifcantly and negatively correlated with pollution level and
these indicative OTUs could be used to predict the water quality status with up to 77% success. Thus, our
multiple approaches combining 18S rDNA amplicon sequencing, co-occurring network and indicator species
analyses suggest that this study gives a novel approach based on microeukaryotic communities to assess and
predict the water quality status of urban aquatic environments.
Yang YG, Chen HH, Abdullah Al M et al.
Urbanization often exerts multiple effects on aquatic and terrestrial organisms, including
changes in biodiversity, species composition and ecosystem functions. However, the impacts of urbanization on river phytoplankton in subtropical urbanizing watersheds remain
largely unknown. Here, we explored the effects of urbanization on phytoplankton community structure (i.e., biomass, community composition and diversity) and function (i.e., resource use effciency) in a subtropical river at watershed scale in southeast China over 6
years. A total of 318 phytoplankton species belonging into 120 genera and 7 phyla were
identifed from 108 samples. Bacillariophyta biomass showed an increasing trend with increasing urbanization level. The phytoplankton community shifted from Chlorophyta dominance in rural upstream waters to Bacillariophyta dominance in urbanized downstream
waters. Furthermore, phytoplankton diversity and resource use effciency (RUE = phytoplankton biomass/total phosphorus) were signifcantly decreased with increasing urbanization level from upstream to downstream. Phytoplankton RUE exhibited a signifcant positive
correlation with species richness, but a negative correlation with phytoplankton evenness.
The variation in environmental factors (turbidity, total nitrogen, NH4+-N, total phosphorus,
PO43−-P and percentage urbanized area) was signifcantly correlated with phytoplankton diversity and RUE. Overall, our results revealed the influence of urbanization on phytoplankton community structure and ecosystem function was due to its altering the environmental conditions. Therefore, human-driven urbanization may play crucial roles in shaping the
structure and function of phytoplankton communities in subtropical rivers, and the mechanism of this process can provide important information for freshwater sustainable uses,
watershed management and conservation.
Abdullah Al M, Akhtar A, Rahman MF et al.
The temporal distribution pattern of zooplankton communities was studied in coastal waters of the
northern Bay of Bengal, Bangladesh, during a 1-year period of investigation (May 2014-April 2015).
Throughout the investigation, a total of 38 zooplankton species were recorded, in details 22 holoplankton and 16 mero-plankton species. Copepods (Acartia danae, Acartia tonsa, Cyclops biscuspidatus,
and Canthocalanus pauper), amphipods (Grandidierella megnae), shrimps (Penaeus indicus and Penaeus
merguiensis), Acetes (Acetes indicus), and mysids (Americamysis bahai) were the dominant zooplankton
taxa. The maximum abundance of total zooplankton and species richness was recorded in monsoon
season whereas abundance of holo-plankton and species diversity was recorded in winter. Multivariate
analyses revealed that the temporal pattern of species distribution of zooplankton communities
significantly differed among the four seasons. RELATE analysis signified that temporal variation in
species distribution and community structure of zooplankton significantly correlated with ecological
condition of water. Moreover, BEST matching analysis indicated that NO2-N along with salinity, rainfall,
transparency, TDS, TSS and pH were the main driving forces for these temporal variations in species
distribution and community composition of zooplankton communities. Finally, correlation analysis
showed that species evenness and diversity significantly correlated with salinity, transparency and TDS.
These results suggest that zooplankton distribution pattern might be shaped by ecological condition of
water in such marine ecosystem and may potentially be used as bioindicators of marine water quality.
